I haven’t seen this issue reported yet, so here goes…
After upgrading the Develop version to 2.0.0.3232, Sonarr no longer removes shows that have been deleted from the Sonarr calendar.
I can see that Sonarr scans for the shows that stay on the calendar when I do a manual “Update Library” but alas, the shows still remain on the calendar even though the entire folder for that show has been deleted.